Fracture toughness of aluminium alloy 7075-T6 in the as-cast condition

Abstract

The fracture toughness of high strength aluminium alloy 7075-T6 in the as-cast condition was studied using standard compact tension specimens with thicknesses ranging from 4 to 25 mm with a 3 mm incremental interval. ASTM Standard E 399-74 for plane strain fracture toughness determination was adhered to in the investigation. The results show that the ASTM-E 399 Standard minimum thickness requirement occurs before the fracture toughness K c reaches the limiting value K Ic but that for the material tested, although K c decreases as the specimen thickness increases within the valid thickness range K Q remains constant and valid over this thickness range and thus K Ic can be determined. The plane strain fracture toughness is 27.5 MPa m 1 2 . K Ic values obtained from specimens of different crack plane orientations were found to remain constant, indicating the lack of anisotropy in the material. This is expected, however, for material in the as-cast condition.